In situ synthesis of Fe2O3/Fe3O4 nanoarray hybrid as highly effective electrocatalysts for alkaline hydrogen evolution

It is of great importance to rationally develop and design cost-effective, high durable and non-noble metal catalysts for electrocatalytic water splitting. Here, self-supported well-defined crystalline iron oxides hybrid (FeO _x /IF) was successfully fabricated by facile in-situ thermal air oxidation of iron foam. An investigation into the effects of thermal oxidation temperature on the crystalline structure and surface appearance of FeO _x/IF was studied. The resultant FeO _x/IF-550 reveals nanoarrays morphology composed of Fe ₂O ₃ and Fe ₃O ₄ hybrid with Fe ₂O ₃ and Fe ₃O ₄ heterojunctions, which exhibits remarkably superior catalytic activity towards HER with a low overpotential of only 98 mV to drive a current density of 10 mA cm ⁻² in alkaline solution. Meanwhile, FeO _x/IF-550 exhibits good durability with negligible attenuation of overpotential at a large current density of 500 mA cm ⁻² for 24 h in alkaline solution. The excellent HER performance of FeO _x/IF is mainly attributed to the synergistic effect of Fe ₂O ₃ and Fe ₃O ₄ , increased accessible active sites and accelerated charge transfer. The present study provides new insights into the design of cost-effective electrocatalysts with high activity and excellent stability for industrialization.